1. Field of the Invention
This invention is concerned with liquid dispensers, such as those used to dispense post-mix soft drinks, and which are required to supply a finished product consisting of two liquids mixed at a predetermined ratio.
2. Description of the Related Art
A conventional dispensing device comprises conduit means for connection to storage devices for each of the two liquids, for connection of the storage means to a mixing chamber for the delivery of liquids to the mixing chamber in which the liquids are mixed and from which the mixture is dispensed, valve means being provided for each liquid, and flow control means being provided to control the relative quantities in which said liquids are delivered to the mixing chamber.
A number of situations may occur which cause the ratio in which the proportions in which the two liquids are delivered to the mixing chamber are varied. For example where the storage means is pressurised for the delivery of the liquids to the mixing chamber, pressure applied to the storage means may vary. Additionally, viscosity of the constituents may vary, particularly where one of the liquids is provided by a syrup.
Conventional flow control means operate on a proportional basis, such that the rate of flow of one of the liquids is gradually reduced by an amount proportional to the perceived divergence of the proportions from the desired mixture, so that the flow rates return to correct proportions, the intention being that the rates of flow of the two liquids along the conduits are as desired in the final mixture. Such flow control systems have heretofore proved to be somewhat unsatisfactory, and it is one of the various objects of this invention to provide a liquid dispensing device in which the relative proportions in which the two liquids are dispensed from the mixing device may be maintained with a high degree of accuracy, despite changing external factors.